The present invention relates to a polishing work holder for supporting a lens to be polished for use in a lens polishing machine.
Such a polishing work holder is disclosed in Japanese Patent Application Laid-open No. 121 862/86 and Japanese Utility Model Application Publication No. 37,627/87.
The former is shown in FIG. 17, in which a polishing dish 60 is rotated and swung, a polishing holder 63 is rotatably supported by a housing 61 through a bearing 62 and is fixed vertically relative to the direction of a sphere center of the polishing dish 60 and a pressure is added thereto in order to polish a lens 64. A spring 65 is attached to a tip portion of the polishing holder 63, thereby elastically pressing the lens 64 between the polishing dish 60 and the polishing holder 63.
The latter is shown in FIG. 18, in which a lens holding device for use in a lens polishing machine include a lens drive lever 67 capable of moving in the horizontal direction while continuously urging in a vertical direction surface of a polishing dish 66 which is rotatably supported about its axis. The lens holding device comprises an inversed cup body 68 rotatably attached at a tip portion of the lens drive lever 67, and a lens receptacle 70 detachably fitted in the inversed cup body 68. The inversed cup body 68 contacts the lens receptacle 70 through an elastic ring 69 so as to tilt by an infinitesimal angle relative to the inversed cup body 68, a recess portion 72 formed at lower surface of the lens receptacle 70. The lens receptacle 70 holds a lens 71 therein, and communicating holes 73, 74 formed in the lens receptacle 70 and supporting shaft of the cup body 68 adhere the lens 71 to the lens receptacle 70 under vacuum suction.
The teachings of (Japanese Patent Application Laid-open No. 121,862/86, however do not provide a mechanism for limiting movement of lens 64 in the radial direction, so that when polishing with fixed abrasive grain wheel or the like, the lens 64 is pulled by polishing resistance in the radial direction and thus the axis of lens becomes excessively shifted.
The (Japanese Utility Model Application Publication No. 37,627/87) teaches that, the lens receptacle 70 limits movement of the lens 71 in the radial direction, and is adhered to the inversed cup body 68 under vacuum suction through the elastic member 69 of rubber or the like, so that as in the former, the entire lens receptacle is pulled in the radial direction because of polishing resistance during the polishing process, and thus the axis of lens becomes shifted. When polishing occurs under such conditions, the movement of lens, that is, the movement of lens receptacle in the horizontal direction and infinitesimal displacement of lens receptacle in the vertical direction can not be adsorbed since the elastic member 69 is in the compressed state between the inversed cup body 68 and the lens receptacle 70. This results in chattering of the lens during polishing and thus machining becomes impossible and the accuracy of the machined surface degraded resulting in the production of many substandard articles.